The overall objective of the project is to explore the phenomenon of memory in lower animals. Memory may be conceptualized as a sequence of events starting with initial sensory input impinging upon an organism with a previously determined perceptual set and terminating at a later time with some behavioral manifestation of the retained information. This orientation attempts to avoid the frequent over-emphasis placed upon "initial fixation" and is consonant with recent data suggesting that experimentally-induced amnesia is often the consequence of a retrieval failure rather than a failure in the establishment or maintenance of storage. The project consists of various studies each designed to produce additional constraints upon the several memory models presently under consideration.